High pressure and hot at both rads and water?

I have a canray 5 oil boiler. The circulation pump had ceased and has now been replaced. However I have some weird problems. The pressure creaps up to 3.2 bar at which point the expansion vessel starts to leak very slightly, tuning the heat setting down keeps the pressure just under 3 bar. The circulation pump constantly runs even when room stat and both heat and water are turned off at the programmer. When the water is set to on I get heat at water and rads. I have to admit that I 'fiddled' with the diverter valve so I am not sure what position this is now in; but even if it is in the wrong position could it have the above effects?